* Optimized internals of Storm to use much fewer threads - two fewer threads per spout and one fewer thread per acker.

* Removed error method from task hooks (to be re-added at a later time)

* Validate that subscriptions come from valid components and streams, and if it's a field grouping that the schema is correct (thanks xumingming)

* Only track errors on a component by component basis to reduce the amount stored in zookeeper (to speed up UI). A side effect of this change is the removal of the task page in the UI.

* Add TOPOLOGY-TICK-TUPLE-FREQ-SECS config to have Storm automatically send "tick" tuples to a bolt's execute method coming from the __system component and __tick stream at the configured frequency. Meant to be used as a component-specific configuration.

* Upgrade Kryo to v2.04